The effect of a cathode micro-porous layer that is composed of carbon powder or carbon nanotubes on cell performance is investigated Polarization curves together with the respective anode and cathode potentials are measured The results show that the cathode potential can be significantly improved with adding a hydrophobic micro-porous layer between the cathode catalyst layer and the gas-diffusion layer The increased performance with the cathode micro-porous layer is mainly attributed to the fact that the cathode water flooding can be alleviated as a result of the reduced water crossover which consequently facilitates the transport of oxygen to the catalyst layer It is also found that a crack-free micro-porous layer made of carbon nanotubes gives a much higher cathode potential compared with a micro-porous layer composed of carbon powder (C) 2010 Elsevier B V All rights reserved